Cable Robot Performance Evaluation by Wrench Exertion Capability

Although cable driven robots are a type of parallel manipulators, the evaluation of their performances cannot be carried out using the performance indices already developed for parallel robots with rigid links. This is an obvious consequence of the peculiar features of flexible cables-a cable can only exert a tensile and limited force in the direction of the cable itself. A comprehensive performance evaluation can certainly be attained by computing the maximum force (or torque) that can be exerted by the cables on the moving platform along a specific (or any) direction within the whole workspace. This is the idea behind the index-called the Wrench Exertion Capability (WEC)-which can be employed to evaluate the performance of any cable robot topology and is characterized by an efficient and simple formulation based on linear programming. By significantly improving a preliminary computation method for the WEC, this paper proposes an ultimate formulation suitable for any cable robot topology. Several numerical investigations on planar and spatial cable robots are presented to give evidence of the WEC usefulness, comparisons with popular performance indices are also provided

Manipulator Performance Measures - A Comprehensive Literature Survey

Due to copyright restrictions of the publisher this item is embargoed and access to the file is restricted until a year after the publishing date.The final publication is available at www.springerlink.comPerformance measures are quintessential to the design, synthesis, study and application of robotic manipulators. Numerous performance measures have been defined to study the performance and behavior of manipulators since the early days of robotics; some more widely accepted than others, but their real significance and limitations have not always been well understood. The aim of this survey is to review the definition, classification, scope, and limitations of some of the widely used performance measures. This work provides an extensive bibliography that can be of help to researchers interested in studying and evaluating the performance and behavior of robotic manipulators. Finally, a few recommendations are proposed based on the review so that the most commonly noticed limitations can be avoided when new performance measures are proposed.http://link.springer.com/article/10.1007/s10846-014-0024-y

Optimal dimensional synthesis of force feedback lower arm exoskeletons

This paper presents multi-criteria design optimization of parallel mechanism based force feedback exoskeletons for human forearm and wrist. The optimized devices are aimed to be employed as a high fidelity haptic interfaces. Multiple design objectives are discussed and classified for the devices and the optimization problem to study the trade-offs between these criteria is formulated. Dimensional syntheses are performed for optimal global kinematic and dynamic performance, utilizing a Pareto front based framework, for two spherical parallel mechanisms that satisfy the ergonomic necessities of a human forearm and wrist. Two optimized mechanisms are compared and discussed in the light of multiple design criteria. Finally, kinematic structure and dimensions of an optimal exoskeleton are decided

Paralleelmehhanismide kinetostaatiliste jõudlusindeksite uuring ning võrdlus

Nii kaua, kui on kasutusel olnud robotid, on käinud teadusuuringud nende kasutamiseks ning töö optimeerimiseks meie igapäevases elus. Samal ajal, kui meie teadmised robotite teemal on suuresti arenenud, on kasvanud ka vastavate struktuuride keerukus. Seega on arendatud mitmeid meetodeid ja indekseid, aitamaks disaneritel ning inseneridel välja selgitada parimad seadmed vastavate ülesannete lahendamiseks. Lisaks on huvi paralleelmehhanismide suunas viimaste aastate jooksul märgatavalt kasvanud. Peamiseks põhjuseks on paljudes valdkondades märgatavalt parem sooritusvõime võrreldes seriaalmanipulaatoritega. Ometi pole arendatud veel ühtegi globaalset jõudlusindeksit, mis võimaldaks täpsuse perspektiivis paralleelmanipulaatorite omavahelise võrdluse. Käesoleva lõputöö fookuseks on kintestaatilise jõuldusindeksi arendustööst ülevaate pakkumine. Uuritav indeks peab robustselt suutma hinnata läbi vastava indeksi paralleelmanipulaatorite täpsust.For as long as we have used robots there has also been ongoing research to allow us to use and improve efficiency of automation in our daily lives. As our knowledge about robots has largely improved, so has the complexity of their structures. Thus, various methods and indices have been developed to help designers and engineers determine the best manipulator for a specific task. In addition, the interest towards parallel manipulators has seen growth in the last couple of years due to significantly better performance in various areas in comparison to serial mechanisms. However, no global performance index to evaluate accuracy and allow comparison in that perspective between parallel mechanisms has been developed. This thesis focuses on giving an overview on the developments towards finding a robust kinematic sensitivity index to measure accuracy performance of parallel manipulators

Design and analysis of kinematically redundant planar parallel manipulator for isotropic stiffness condition

Parallel manipulators are a form of closed loop linkages and have a wide range of applications e.g. surgical robots, flight simulators, pointing devices etc. Parallel mechanisms have many advantages over serial manipulator. Higher accuracy, stiffness and increased payload capacity are the characteristics of parallel manipulator. In spite of many advantages, they have limited workspace and more singularity regions. So, redundant architectures have become popular. However, redundancy leads to infinite solutions for inverse kinematic problem. The current work addresses this issue of resolving the redundancy of kinematically redundant planar parallel manipulators using optimization based approach. First the conventional non-redundant 3-RPR planar parallel manipulator is presented. Afterwards the kinematically redundant counterpart 3-PRPR is discussed and actuation redundant 4-RPR has been touched upon briefly. Computer simulations have been performed for the kinematic issues using MATLAB programme . The workspace of redundant and non-redundant parallel manipulators have been obtained. The generalized stiffness matrix has been derived based upon the Jacobian model and the principle of duality between kinematics and statics. A stiffness index has been formulated and the isotropy of stiffness index is used as the criterion for resolving redundancy. A novel spiral optimization metaheuristics has been used to achieve the isotropic stiffness within the selected workshape and the results are compared against particle swarm optimization. The results obtained from the novel Spiral optimization are found to be more effective and closer to the objective function as compared to the particle swarm optimization. Optimum redundant parameters are obtained as a result of the analysis. A wooden skeletal prototype has also been fabricated to enhance the understanding of the mechanism workability

Dimensional synthesis of a spherical parallel manipulator based on the evaluation of global performance indexes

In this work, the dimensional synthesis of a spherical Parallel Manipulator (PM) with a -1S kinematic chain is presented. The goal of the synthesis is to find a set of parameters that defines the PM with the best performance in terms of workspace capabilities, dexterity and isotropy. The PM is parametrized in terms of a reference element, and a non-directed search of these parameters is carried out. First, the inverse kinematics and instantaneous kinematics of the mechanism are presented. The latter is found using the screw theory formulation. An algorithm that explores a bounded set of parameters and determines the corresponding value of global indexes is presented. The concepts of a novel global performance index and a compound index are introduced. Simulation results are shown and discussed. The best PMs found in terms of each performance index evaluated are locally analyzed in terms of its workspace and local dexterity. The relationship between the performance of the PM and its parameters is discussed, and a prototype with the best performance in terms of the compound index is presented and analyzed

Kinematics and Robot Design I, KaRD2018

This volume collects the papers published on the Special Issue “Kinematics and Robot Design I, KaRD2018” (https://www.mdpi.com/journal/robotics/special_issues/KARD), which is the first issue of the KaRD Special Issue series, hosted by the open access journal “MDPI Robotics”. The KaRD series aims at creating an open environment where researchers can present their works and discuss all the topics focused on the many aspects that involve kinematics in the design of robotic/automatic systems. Kinematics is so intimately related to the design of robotic/automatic systems that the admitted topics of the KaRD series practically cover all the subjects normally present in well-established international conferences on “mechanisms and robotics”. KaRD2018 received 22 papers and, after the peer-review process, accepted only 14 papers. The accepted papers cover some theoretical and many design/applicative aspects